Despite the reports of its impending death, coal-fired electricity generation is not leaving anytime soon. Check out this graph that PJM released today:
It shows what technologies we will be using to produce electricity five years from now in 2023. Notice that oil, wind, hydro and solar all stay about the same: just over 10% of the total generation fleet.
Nuclear drops slightly from just under 20% today to maybe 17-18% in 2023. Quick guess is that accounts for closing Exelon's Oyster Creek in New Jersey and Three Mile Island in Pennsylvania. I don't believe anything else is decommissioning in PJM before then.
Gas increases significantly from ~40% today to more than 45% then. PJM has said it can remain reliable with upwards of 86% gas, but that's still a pretty big number.
Finally, look at coal: Yes, it'll be down from ~31% to about 28%. But 30% is still a lot of megawatt-hours.
One final point... these numbers may not be guaranteed, but they're pretty close. PJM holds its capacity auctions three years in advance, so the auction that happened last May was for the 2020/21 delivery year. The Base Residual Auction (BRA) this May will be for 2021/22, so we'll get a more precise number then.